feat(anthropic): support webfetch tool

[christian-bromann]

This PR adds support for Anthropic's Web Fetch tool (web_fetch_20250910) to @langchain/anthropic, enabling Claude to retrieve full content from specified web pages and PDF documents.

Usage

import { ChatAnthropic, tools } from "@langchain/anthropic";

const model = new ChatAnthropic({
  model: "claude-sonnet-4-5",
  clientOptions: {
    defaultHeaders: { "anthropic-beta": "web-fetch-2025-09-10" },
  },
});

// Basic usage
const response = await model.invoke(
  "Analyze the content at https://example.com/article",
  { tools: [tools.webFetch_20250910()] }
);

// Combined with web search
const response = await model.invoke(
  "Find articles about AI and analyze the most relevant one",
  {
    tools: [
      tools.webSearch_20250305({ maxUses: 3 }),
      tools.webFetch_20250910({ maxUses: 5, citations: { enabled: true } }),
    ],
  }
);

Notes

• Requires beta header anthropic-beta: web-fetch-2025-09-10
• ⚠️ Security consideration: Only use in trusted environments or when handling non-sensitive data (see docs)

Related

• Anthropic Web Fetch Documentation

[changeset-bot]

🦋 Changeset detected

Latest commit: 6f83fef

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@langchain/anthropic	Patch

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[hntrl]

Assuming that your note about needing the beta flag in the chat model initializer is a red herring -- adding the tool type to that betas map should add those beta flags automatically

[christian-bromann]

@hntrl good call, removed the note to avoid confusion.